By Kelly A. Reynolds, MSPH, PhD
Very little is known about the emerging pathogen, Elizabethkingia. A sudden increase in cases in the Midwestern region of the US has officials scrambling to identify reservoirs of the bacteria that may contribute to its survival and transmission. So far, there remain more questions than answers.
What is Elizabethkingia?
Elizabethkingia is a bacterium belonging to the family of Flavobacteriacea, which are widespread in nature and thus, commonly found in water, soil, food and clinical samples. Elizabethkingia strains are more commonly found in freshwater and marine environments. The name comes from Elizabeth King, who first identified the bacteria in 1959 while at the US Centers for Disease Control and Prevention.
Very few studies have been conducted on environmental species as they’ve had rare clinical significance.(1) Previously, the bacteria have been isolated from condensation water. Like the more well-known Legionella bacteria, they have also been associated with internalization in free living amoeba, which may protect them in aqueous environments.
An outbreak is generally defined as at least two cases of illness. In the past, Elizabethkingia infections rarely occurred two at a time and therefore, did not constitute outbreak status. Previous cases were primarily tracked to hospitals where the infection was acquired mostly by the immunocompromised from exposure in healthcare facilities. Infections typically occur in the blood stream and more rarely in the respiratory system or joints. Symptoms include headache, fever, cough, shortness of breath, chills, joint pain and skin infection (cellulitis). Some species also cause serious neonatal infections resulting in meningitis and sepsis. Most patients are over the age of 65 and suffer from at least one underlying serious condition that weakens their immunity and increases their vulnerability to infections of all types. Treating Elizabethkingia infections can be difficult as it is resistant to some antimicrobial treatments. Isolates have been found that are multidrug-resistant; however, effective treatments and treatment combinations have been identified, improving the outcomes for infected patients.
A deadly outbreak in Wisconsin
Recently something shifted in the epidemiology of Elizabethkingia. An outbreak was documented in the US beginning in Wisconsin. While illnesses had been documented previously, they were typically healthcare-acquired and at a low, randomly dispersed rate of five to 10 cases per year. Suddenly a strain of Elizabethkingia anopheles was identified in 59 confirmed illness cases, with four more possible victims. Of these cases, 19 resulted in death (18 confirmed and one suspected case)(2). The highly fatal infections in Wisconsin were not hospital-acquired but rather from a community-acquired source. One commonality is that victims of the current outbreak are also generally immunocompromised (i.e., elderly or suffering from chronic illnesses) and more vulnerable to infections. The E. anopheles species from the Wisconsin outbreak is somehow associated with mosquitoes. The bacteria was first isolated from the gut of the Anopheles gambiae mosquito in 2011.(3) Experts still do not know, however, if mosquitoes play a role in transmission of the bacteria. Related strains to the Wisconsin outbreak have also been confirmed in Michigan and Illinois.
Investigating causes
So how did this bacteria suddenly emerge? No one really knows why Elizabethkingia cases have suddenly increased. As of press time, environmental sources of the Wisconsin outbreak have not been identified. The first cases were reported around November 2015, which prompted a CDC investigation in January 2016. According to the CDC, this is the first E. anopheles outbreak they have investigated. Evidence surrounding the outbreak, including the genetic relatedness of the outbreak strain among those infected, suggests a common source of exposure. Therefore, experts naturally suspected a waterborne route of transmission but patients in the current outbreak are from 13 different counties, including: Columbia, Dane, Dodge, Fond du Lac, Jefferson, Milwaukee, Ozaukee, Racine, Sauk, Sheboygan, Washington, Waukesha and Winnebago, served by as many drinking water sources, including private wells.
The Wisconsin Department of Health Services (DHS) Division of Public Health and the CDC are conducting interviews with patients and their families to try and find clues related to their behaviors or possible exposures in food, water or other suspected environments. So far, investigations show no common source of residence, healthcare delivery or personal products (i.e., skin care products or over-the-counter medications) among the infected, nor does the infection seem to spread to other family members. Person-to-person contact does not seem likely given that infected patients remain positive for the bacteria on their skin and in their throat even after they feel well again and nose and throat swabs of close family contacts have been negative.
A new strain kills in Illinois
As of April 20, no more cases have been reported related to the Wisconsin outbreak. There is a new cluster of cases, however, emerging in Illinois. These new cases are from a genetically distinct strain of the Elizabethkingia bacteria. In the Illinois outbreak, 10 people have been infected, resulting in six deaths. Similar to Wisconsin, most had other underlying health conditions.(4) Representatives from the CDC indicate that additional cases may not be due to a true incidence increase but rather to better reporting and increased awareness of Elizabethkingia. While this may be true, the fact that we missed outbreaks before should be equally alarming.
Preventing transmission
For now, health officials say the general public should not be concerned. Infection rates are still very low. The high mortality rate (approximately one third) in the infected, however, is troubling. The CDC recommends that people wash their hands as the primary precaution for Elizabethkingia prevention. Until the transmission path is identified, recommendations for control will remain vague. Healthcare providers should be on the alert to recognize infections so that they can be treated quickly and with the proper medications for optimum outcomes.
Although a water-based route has not been found, elements of the current outbreaks are consistent with other pathogens where an environmentally ubiquitous organism (common to soil and water) colonizes water supplies and targets the immunocompromised. The stories of Legionella, Mycobacterium and Psuedomonas are similar. A more conservative approach is to acknowledge that until tap water is ruled out as a source, we must still consider the benefits of POU/POE treatments effective for bacterial removal.
References
(1) Dworkin, M.; Falkow, S.; Rosenberg, E.; Schleifer, K.-H. and Stackebrandt, E. Eds., The Prokaryotes. New York, NY: Springer New York, 2006.
(2) ProMED, “Elizabethkingia anophelis-USA (12): (Wisconsin, Illinois) fatal, community acquired,” ProMED Digest, Vol. 46, No. 58, 21-Apr-2016.
(3) Kämpfer, P.; Matthews, H.; Glaeser, S.P.; Martin, K.; Lodders, N. and Faye, I. “Elizabethkingia anophelis sp. nov., isolated from the midgut of the mosquito Anopheles gambiae,” Int. J. Syst. Evol. Microbiol., Vol. 61, No. Pt 11, pp. 2670–5, Nov. 2011.
(4) llinois-CNN.com, CNN, 2016. [Online]. Available: www.cnn.com/2016/04/20/health/elizabethkingia-illinois-cluster/. [Accessed: 21-Apr-2016].
About the author
Dr. Kelly A. Reynolds is an Associate Professor at the University of Arizona College of Public Health. She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached at reynolds@u.rizona.edu